The broad aims of the proposed project are to obtain more information about synaptic organization and function in the vertebrate central nervous system and to correlate this information with changes in the behavior of the animal induced by behavioral classical conditioning. The lamprey, a jawless fish, has been chosen as the experimental animal because it is a convenient size for behavior work and has the unique property for a vertebrate of having large identifiable nerve cells and fibers which are visible in the living central nervous system and can be readily impaled with micropipettes. Specifically, it is proposed first to study the characteristics of behavioral classical conditioning in the lamprey, an animal which has received little or not previous behavior investigation. When the optimum conditions for obtaining conditioning in this animal have been determined, intracellular recordings will be obtained from conditioned animals in order to determine if any of the large cells in the central nervous system are involved in the learned performance. Specifically, it will be determined whether the large Muller cells in the brain stem change their firing characteristics as a result of conditioning. If this proves to be true, then an attempt will be made to simulate the conditioning situation while recording intracellularly from the cell bodies of Muller cells. The aim is to record the changes in synaptic potentials (produced by the conditioned stimulus) as a function of conditioning stimulation. Studies on the functional organization of lamprey brain, particularly the trigeminal sensory and motor systems, will be continued.